1. Field of the Invention
This invention relates to solid sulfides and selenides, and more particularly to such compounds containing one or more rare earth element and hafnium or zirconium.
2. Description of the Prior Art
Ternary sulfides and selenides of the rare earths have been known for both the lanthanide and actinide series. Compositions of the formula Ce.sub.2 US.sub.5, Gd.sub.2 US.sub.5, Pu.sub.2 US.sub.5 as well as U.sub.3 S.sub.5 (i.e., U.sub.2.sup.III U.sup.IV S.sub.5) have been disclosed by Marcon et al. in Rev. Int. Hautes Temper. et Refract, t. 5, pp 51-54 (1968). The crystal structure was recognized to be orthorhombic. A detailed structural analysis was made for U.sub.3 Se.sub.5 by Moseley et al. in Acta Cryst., B28, pp. 1816-1821 (1972) and for U.sub.3 S.sub.5 by Potel et al. in C. R. Acad. Sc. Paris, t. 275, pp 1419-1421 (1972).